Effective electrostatic potential between two oppositely charged cylinder rods in primitive model and extended primitive model electrolytes

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The classical density functional theory, combined with a fundamental measure functional and a second order functional perturbation truncation, is employed to study effective electrostatic potential between two oppositely and asymmetrically or symmetrically charged cylinder rods in electrolyte solution modeled by the primitive model and extended primitive model, respectively. We investigate how strength and distance of a peculiar repulsion peak are modulated by the influencing factors such as rod charge strength, rod charge strength asymmetry, salt concentration, interionic neutral and non-hard sphere interactions, and ion electric valence and size. We acquire a dozen change patterns of the repulsion peak strength and peak distance with system parameters and draw out normative as well as raw empirical implications of the repulsion mechanism based on the idea of excess adsorption-induced osmotic pressure difference by augmenting the abstract idea by the electric neutrality principle and concepts such as tightness or compression of the ion layer, crowding of the surface region, and multiplayer in the ion distribution. The observed rich diversity of the possible effective electrostatic potential between the two oppositely and asymmetrically or symmetrically charged rods increases the options to optimize the interactions for specific purposes.